1. Field of the Invention
This invention relates to particulate product filling machines for packaging food products and the like. More particularly, the present invention relates to an improved following system for a particulate product filler which allows higher production line speeds while maintaining volumetric accuracy.
2. State of the Art
Particulate food products typically involve a variety of individual pieces mixed together, sometimes with a liquid or sauce. Examples of particulate food products include cooked rice, diced vegetables, stir fry vegetables, fruit pieces or fruit cocktail, and various pasta dishes. In the food processing industry, these products may be packaged in a wide variety of containers such as cups, trays, bottles, pouches, etc., which are formed of paper, plastic, or foil. However, the packaging of particulate food products requires special care to prevent large pieces--e.g., the noodles, fruit, or vegetables, etc.--from being chopped or mashed during packaging. For this reason, many of these types of food products are still portioned and packaged by hand. Such an operation typically involves a large number of workers each using a spoon or scoop to place a single portion of food in each container as it passes by on a conveyor. Obviously, this method presents several drawbacks. It involves substantial labor cost; portions tend to be irregular; there is the higher possibility of contamination of the food product by worker contact than with mechanical methods; and it presents a likelihood of fatigue and repetitive motion injuries to workers.
To avoid these sorts of problems, mechanical measuring and filling machines have been developed for particulate food products. These machines typically involve a measuring and discharge head which is positioned above a conveying device such as a conveyor belt. The conveyor moves empty open containers past the discharge head at some constant rate, and the product is portioned and dropped into each container as it passes by. The containers may move past more than one such machine if multiple products are to be placed therein, and then they typically proceed to an additional machine which places a top seal or cap on the container to seal it. These types of particulate product filling machines help ensure precise portion measurements, and also avoid the cost, cleanliness, and other drawbacks of hand packaging.
However, conventional particulate product packaging machines known in the art suffer from several drawbacks. First, in order to avoid damaging the product, it is usually allowed to flow from the machine into the open package purely under the force of gravity alone. Because direct mechanical force is not used to move the product, the speed at which the product can be placed into the container is thus limited by the physical characteristics of the product. For example, a viscous product such as spaghetti will discharge from the machine relatively slowly. The production line speed and output rate are thus limited because the conveyor carrying the containers can move past the machine outlet no faster than each discrete portion of the product can drop therefrom. Even when an air jet or other means is used to help discharge the product from the discharge opening, there is still a relatively low speed limit on the rate of production.
As an operative example, using conventional particulate product filling machines to place cooked rice of a given consistency, stickiness, etc. into containers having a 5" long opening, the containers being spaced out every 10" along a conveyor belt, the top speed of the line is approximately 73 containers per minute. Any higher speed begins to cause spillage, which not only causes contamination of the work environment, but, more importantly, contaminates the container edge, preventing a proper seal and resulting in wasted product. Obviously, this speed limit increases the cost and reduces the profitability of particulate product packaging operations.
To speed up the process, particulate product filling machines have been developed which employ a bucket follower system, or what is known as a walking beam or walking head system. These machines are often used for adding sauces to certain food products, and typically involve an assembly of buckets or other discharge apparatus which follow a container for some period of time as it moves along the conveyor. By briefly following the moving container, the window of time for discharge is increased relative to the conveyor speed, thus allowing a higher line speed.
However, bucket following systems do not solve all of the problems associated with particulate products, and introduce some additional problems as well. First, while bucket following systems can operate faster than static systems, they cannot do so and simultaneously provide a clean discharge, especially for sticky products such as cooked rice or spaghetti. Second, bucket following systems are inflexible because they are mechanically linked to the conveyor line, and speed up or slow down solely in response to the speed of the conveyor line. Because of this condition, they always place the product in the same place in the container. Changing the product placement would require the removal and replacement of many mechanical components such as cams, sprockets, gears, etc. Additionally, their speed cannot be adjusted based on, for example, a sudden change in container spacing, such as could occur if one of two lines supplying empty containers to the conveyor goes down. Third, bucket follower systems may involve anywhere from 2 to 20 or more buckets, all of which must be routinely cleaned, and which must each be removed and replaced whenever a product or container is changed, because each different container size and shape requires a different bucket. This makes the changeover from one product to another very time consuming.
It would therefore be desirable to have a particulate product filling apparatus which overcomes the discharge speed limitations of known particulate product filling machines, and also avoids the cleanliness and flexibility problems of bucket follower systems. Such a machine could accommodate faster line speeds for all types of particulate products without damaging the product or creating an unclean environment.